According to the present invention, a continuous form web is cut lengthwise in the direction of web travel and interstacked such that a pair of continuous webs overlap one another, with the forms of the overlapped webs being longitudinally offset one from the other. The interstacked continuous webs initially pass between a pair of slow rollers, one of which, preferably the upper roller, is mounted for movement toward and away from the lower roller, i.e., has an eccentric movement, to close and open the nip between the rollers. Subsequently, the interstacked webs pass into the nip of a pair of downstream rollers selectively driven at a speed comparable to the speed of the upstream slow rollers and a faster speed. A breaker bar is disposed between the pairs of rollers along the path of movement of the interstacked webs.
When the leading portion of one web passes through the downstream roller pair, and the transverse line of perforations of the one web is aligned substantially with the breaker bar, the eccentrically mounted low speed roller closes on the overlapped webs. Substantially simultaneously, the downstream rollers are also rotated at a higher speed relative to the slow speed rollers. The web between the roller pairs is thus tensioned against the breaker bar such that the breaker bar bursts the form along the transverse line of perforations. The downstream rollers quickly move the burst form from the bursting engine whereupon the leading portion of the other web is passed into the nip of the downstream rollers. Similar action occurs with the eccentric slow speed roller closing upon the overlapped webs to enable the form of the other web to be tensioned and burst. It will be appreciated that when the overlying web is engaged between the roller pairs, only the overlying web is tensioned and burst. Likewise, when the underlying web is engaged between the roller pairs, only the underlying web is tensioned and burst. Also, the nip between the rollers of the low speed roller pair is maintained open for the majority of each revolution. In this manner, upstream tractors normally feed the webs through the open nip whereby web pillowing or bubbling effects are avoided.
In a preferred embodiment according to the present invention, there is provided an apparatus for bursting interstacked, longitudinally offset, form sets from continuous webs, comprising a frame, a carriage carried by the frame for longitudinal sliding movement and a first pair of rollers carried by the carriage for rotation at a predetermined speed, the first pair of rollers being positioned to receive the interstacked form sets of the continuous webs between the rollers. At least one roller of the first pair of rollers is arranged to be intermittently moved into and out of engagement with the continuous interstacked web of form sets received between the rollers. A breaker blade is carried by the frame and a second pair of rollers is carried by the frame downstream from the first pair of rollers, the second pair of rollers alternately engaging leading portions of the interstacked form sets and being rotatable at a speed relative to the predetermined speed of the first pair of rollers to create a web tension sufficient to enable bursting of the web into individual forms when the one roller of the first pair of rollers engages the form sets.
In a further preferred embodiment according to the present invention, apparatus is provided for continuously alternately bursting at least first and second webs in an overlapped, longitudinally offset, arrangement of the webs, comprising a frame, first nipping elements carried by the frame and located to receive the webs therebetween at least one of the first nipping elements being selectively movable toward and away from another of the first nipping elements for alternately closing against and releasing the webs therebetween. Second nipping elements are carried by the frame for alternately engaging leading portions of each of the first and second webs, and means for moving second nipping elements when one of the first nipping elements is closed against the webs to create a web tension sufficient to burst individual forms from the one web.
In a still further preferred embodiment according to the present invention, there is provided a method for bursting interstacked longitudinally offset form sets from continuous webs thereof, comprising the steps of feeding the interstacked form sets between a first pair of rollers mounted for rotation at a predetermined speed, alternately feeding leading portions of the interstacked form sets through the nip of a second pair of rollers downstream from the first pair of rollers, disposing a breaker blade between the first pair of rollers and the second pair of rollers, intermittently moving one of the rollers of the first pair of rollers into and out of engagement with the continuous interstacked web of form sets between the rollers of the first pair thereof and rotating the second pair of rollers at a speed in excess of the speed of rotation of the first pair of rollers when one roller of the first pair thereof lies in engagement with the continuous interstacked web of form sets to create sufficient web tension between the first pair of rollers and the second pair of rollers to enable bursting of the web into individual forms.
Accordingly, it is a primary object of the present invention to provide novel and improved apparatus and methods for bursting interstacked longitudinally offset form sets from continuous webs.